Bispecific Antibodies Specifically Binding to Klebsiella Pneumoniae O2 Antigen and O1 Antigen and Compositions Thereof

Abstract

The present application pertains to antibodies or antigen-binding fragments that specifically bind to Klebsiella pneumoniae (K. pneumoniae) O2 antigen, antibodies or antigen-binding fragments that specifically bind to K. pneumoniae O1 antigen, and bispecific antibodies that specifically bind to K. pneumoniae O2 antigen and K. pneumoniae O1 antigen, and pharmaceutical compositions comprising the antibodies or antigen-binding fragments and/or bispecific antibodies, as well as methods of manufacture and uses thereof.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . An isolated antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen, comprising:
 (i) a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 5; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 8, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   (ii) a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 3, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 9, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;   (iii) a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 13, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;   (iv) a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 11, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16, or   (v) a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15.   
     
     
         3 . The isolated antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen of  claim 2 , comprising:
 (i) a V H  comprising the amino acid sequence of SEQ ID NO: 17, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 17; and a V L  comprising the amino acid sequence of SEQ ID NO: 21, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 21;   (ii) a V H  comprising the amino acid sequence of SEQ ID NO: 18, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 18; and a V L  comprising the amino acid sequence of SEQ ID NO: 22, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 22;   (iii) a V H  comprising the amino acid sequence of SEQ ID NO: 19, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19; and a V L  comprising the amino acid sequence of SEQ ID NO: 23, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 23;   (iv) a V H  comprising the amino acid sequence of SEQ ID NO: 19, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19; and a V L  comprising the amino acid sequence of SEQ ID NO: 24, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24; or   (v) a V H  comprising the amino acid sequence of SEQ ID NO: 20, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20; and a V L  comprising the amino acid sequence of SEQ ID NO: 25, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25.   
     
     
         4 . (canceled) 
     
     
         5 . The isolated antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to claim  2 - 4 , wherein
 (i) the antibody or antigen-binding fragment comprises an Fc fragment; and/or   (ii) the antibody or antigen-binding fragment is a full-length IgA, IgD, IgE, IgG or IgM antibody; and/or   (iii) the antibody or antigen-binding fragment is a full-length IgG1, IgG2, IgG3 or IgG4 antibody; and/or   (iv) the antibody or antigen-binding fragment is chimeric, human, or humanized; and/or   (v) the antigen-binding fragment is selected from the group consisting of Fab, Fab′, F(ab)′2, Fab′-SH, single-chain Fv (scFv), Fv fragment, dAb, Fd, or diabody.   
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . (canceled) 
     
     
         9 . (canceled) 
     
     
         10 . A bispecific antibody comprising a first antigen-binding domain specifically binding to  K. pneumoniae  O2 antigen, and a second antigen-binding domain specifically binding to  K. pneumoniae  O1 antigen,
 wherein the first antigen-binding domain comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 11; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 10; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and/or   wherein the second antigen-binding domain comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 35; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 41; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 36; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 42; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46.   
     
     
         11 . (canceled) 
     
     
         12 . (canceled) 
     
     
         13 . The bispecific antibody of  claim 10 , wherein:
 (a) the first antigen-binding domain comprises a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 11, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;   and wherein the second antigen-binding domain comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 35, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 41, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (b) the first antigen-binding domain comprises a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 11, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;   and wherein the second antigen-binding domain comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 36, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a V L  Comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 42, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46; or   (c) the first antigen-binding domain comprises a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and wherein the second antigen-binding domain comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 35, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a V L  Comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 41, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (d) the first antigen-binding domain comprises a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and wherein the second antigen-binding domain comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 36, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 42, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46.   
     
     
         14 . The bispecific antibody of  claim 10 , comprising a first antigen-binding domain specifically binding to  K. pneumoniae  O2 antigen, and a second antigen-binding domain specifically binding to  K. pneumoniae  O1 antigen, wherein the first antigen-binding domain comprises:
 (a) a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24 or 33; or   (b) a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34; and/or   wherein the second antigen-binding domain comprises:   (a) a VH comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a VL comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53; or   (b) a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54.   
     
     
         15 . (canceled) 
     
     
         16 . The bispecific antibody of  claim 14 , wherein:
 (a) the first antigen-binding domain comprises: a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24 or 33; and wherein   the second antigen-binding domain comprises: a V H  Comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  Comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53; or   (b) the first antigen-binding domain comprises: a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  Comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24 or 33; and wherein   the second antigen-binding domain comprises: a V H  Comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  Comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54; or   (c) the first antigen-binding domain comprises: a V H  Comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34; and wherein   the second antigen-binding domain comprises: a V H  comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53; or   (d) the first antigen-binding domain comprises: a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34; and wherein   the second antigen-binding domain comprises: a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54.   
     
     
         17 . (canceled) 
     
     
         18 . (canceled) 
     
     
         19 . The bispecific antibody of  claim 10 , wherein the bispecific antibody has the formats selected from the group consisting of DVD-Ig, Bs4Ab, Hetero H, CrossMab, IgG-(scFv) 2  and scFv-Fab IgG. 
     
     
         20 . The bispecific antibody of any-n-Re-claims  40 - 19 , comprising four polypeptide chains selected from (i) or (ii):
 (i) wherein two of the polypeptide chains comprise V H 1-L-V H 2-C H 1 Structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O2 antigen; V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O1 antigen; L is a peptide linker; C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains; and   the other two of the polypeptide chains comprise V L 1-L-V L 2-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pneumoniae  O2 antigen; V L 2 is a light chain variable domain specifically binding to  K. pnewmoniae  O1 antigen; L is a peptide linker; C L  is a light chain constant domain; or   (ii) wherein two of the polypeptide chains comprise V H 1-L-V H 2-C H 1 structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O1 antigen; V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O2 antigen; L is a peptide linker: C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains; and   the other two of the polypeptide chains comprise V L 1-L-V L 2-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pneumoniae  O1 antigen; V L 2 is a light chain variable domain specifically binding to  K. pneumoniae  O2 antigen; L is a peptide linker: C is a light chain constant domain:   or   preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 61, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 61; and   the amino acid sequence of SEQ ID NO: 62, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 62;   or   (ii) the amino acid sequence of SEQ ID NO: 63, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 63; and   the amino acid sequence of SEQ ID NO: 64, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 64;   or   (iii) the amino acid sequence of SEQ ID NO: 65, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 65; and   the amino acid sequence of SEQ ID NO: 66, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 66:   or   (iv) the amino acid sequence of SEQ ID NO: 67, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 67; and   the amino acid sequence of SEQ ID NO: 68, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 68;   or   more preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 86, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 86; and   the amino acid sequence of SEQ ID NO: 62, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 62:   or   (ii) the amino acid sequence of SEQ ID NO: 87, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 87; and   the amino acid sequence of SEQ ID NO: 64, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 64;   or   (iii) the amino acid sequence of SEQ ID NO: 88, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 88; and   the amino acid sequence of SEQ ID NO: 66, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 66;   or   (iv) the amino acid sequence of SEQ ID NO: 89, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 89; and   the amino acid sequence of SEQ ID NO: 68, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 68:   or   (v) the amino acid sequence of SEQ ID NO: 115, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 115; and   the amino acid sequence of SEQ ID NO: 66, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 66.   
     
     
         21 . (canceled) 
     
     
         22 . (canceled) 
     
     
         23 . (canceled) 
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . (canceled) 
     
     
         28 . (canceled) 
     
     
         29 . (canceled) 
     
     
         30 . (canceled) 
     
     
         31 . The bispecific antibody of  claim 19 , comprising four polypeptide chains:
 (i) wherein two of the polypeptide chains comprise V H 1-C H 1-L1-V H 2-L3-V L 2 structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O2 antigen; V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O1 antigen; L1 and L3 are peptide linkers; C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains; and   the other two of the polypeptide chains comprise V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pnewmoniae  O2 antigen, C L  is a light chain constant domain; or   (ii) wherein two of the polypeptide chains comprise V H 1-C H 1-L1-V H 2-L3-V L 2 structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O1 antigen; V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O2 antigen; L1 and L3 are peptide linkers: C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains; and   the other two of the polypeptide chains comprise V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pneumoniae  O1 antigen, C L  is a light chain constant domain:   or   preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 69, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 69; and   the amino acid sequence of SEQ ID NO: 70, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 70;   or   (ii) the amino acid sequence of SEQ ID NO: 71, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 71; and   the amino acid sequence of SEQ ID NO: 72, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 72;   or   (iii) the amino acid sequence of SEQ ID NO: 73, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 73; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74:   or   (iv) the amino acid sequence of SEQ ID NO: 75, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 75; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74;   or   more preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 90, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 90; and   the amino acid sequence of SEQ ID NO: 70, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 70;   or   (ii) the amino acid sequence of SEQ ID NO: 91, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 91; and   the amino acid sequence of SEQ ID NO: 72, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 72;   or   (iii) the amino acid sequence of SEQ ID NO: 92, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 92; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74;   or   (iv) the amino acid sequence of SEQ ID NO: 93, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 93; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74.   
     
     
         32 . (canceled) 
     
     
         33 . (canceled) 
     
     
         34 . (canceled) 
     
     
         35 . (canceled) 
     
     
         36 . (canceled) 
     
     
         37 . (canceled) 
     
     
         38 . (canceled) 
     
     
         39 . (canceled) 
     
     
         40 . (canceled) 
     
     
         41 . The bispecific antibody of  claim 19 , comprising four polypeptide chains:
 (i) wherein one of the polypeptide chains comprises V H 1-C H 1 Structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O2 antigen; C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains;   one of the polypeptide chains comprises V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pneumoniae  O2 antigen, C L  is a light chain constant domain;   one of the polypeptide chains comprises V H 2-C L  structure from N-terminus to C-terminus, wherein V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O1 antigen; C L  is a light chain constant domain; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains; and   one of the polypeptide chains comprises V L 2-C H 1 structure from N-terminus to C-terminus, wherein V L 2 is a light chain variable domain specifically binding to  K. pnewmoniae  O1 antigen, C H 1 is a heavy chain constant domain 1;   or   (ii) wherein one of the polypeptide chains comprises V H 1-C H 1 structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O1 antigen; C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains:   one of the polypeptide chains comprises V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pneumoniae  O1 antigen; C H 1 is a light chain constant domain;   one of the polypeptide chains comprises V H 2-C L  structure from N-terminus to C-terminus, wherein V H 2 is a heavy chain variable domain specifically binding to  K. pneumoniae  O2 antigen; C H 1 is a light chain constant domain: wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains; and   one of the polypeptide chains comprises V L 2-C H 1 structure from N-terminus to C-terminus, wherein V L 2 is a light chain variable domain specifically binding to  K. pneumoniae  O2 antigen, C H 1 is a heavy chain constant domain 1;   or   preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 76, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 76; and   the amino acid sequence of SEQ ID NO: 77, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 77; and   the amino acid sequence of SEQ ID NO: 78, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 78; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74;   or   (ii) the amino acid sequence of SEQ ID NO: 79, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 79; and   the amino acid sequence of SEQ ID NO: 80, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 80; and   the amino acid sequence of SEQ ID NO: 78, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 78; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74;   or   more preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 94, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 94; and   the amino acid sequence of SEQ ID NO: 77, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 77; and   the amino acid sequence of SEQ ID NO: 95, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 95; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74;   or   (ii) the amino acid sequence of SEQ ID NO: 96, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 96; and   the amino acid sequence of SEQ ID NO: 80, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 80; and   the amino acid sequence of SEQ ID NO: 95, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 95; and   the amino acid sequence of SEQ ID NO: 74, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 74.   
     
     
         42 . (canceled) 
     
     
         43 . (canceled) 
     
     
         44 . (canceled) 
     
     
         45 . (canceled) 
     
     
         46 . (canceled) 
     
     
         47 . The bispecific antibody of  claim 19 , comprising four polypeptide chains:
 (i) wherein two of the polypeptide chains comprise V H 1-C H 1-C H 2-C H 3-L-V H 2-L3-V L 2 structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O2 antigen; V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O1 antigen; V L 2 is a light chain variable domain specifically binding to  K. pneumoniae  O1 antigen; L and L3 are peptide linkers; C H 1 is a heavy chain constant domain 1; C H 2 is a heavy chain constant domain 2; C H 3 is a heavy chain constant domain 3; and   the other two of the polypeptide chains comprise V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pnewmoniae  O2 antigen, C L  is a light chain constant domain;   or   (ii) wherein two of the polypeptide chains comprise V H 1-C H 1-C H 2-C H 3-L-V H 2-L3-V L 2 structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O1 antigen; V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O2 antigen; V L 2 is a light chain variable domain specifically binding to  K. pneumoniae  O2 antigen; L and L3 are peptide linkers: C H 1 is a heavy chain constant domain 1; C H 2 is a heavy chain constant domain 2; C H 3 is a heavy chain constant domain 3; and   the other two of the polypeptide chains comprise V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pnewmoniae  O1 antigen, C L  is a light chain constant domain;   or   preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 97, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 97; and   the amino acid sequence of SEQ ID NO: 83, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 83;   or   (ii) the amino acid sequence of SEQ ID NO: 98, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 98; and   the amino acid sequence of SEQ ID NO: 85, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 85.   
     
     
         48 . (canceled) 
     
     
         49 . (canceled) 
     
     
         50 . (canceled) 
     
     
         51 . The bispecific antibody of  claim 19 , comprising three polypeptide chains:
 (i) wherein one of the polypeptide chains comprises V H 1-C H 1 Structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O2 antigen; C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains;   one of the polypeptide chains comprises V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pneumoniae  O2 antigen, C L  is a light chain constant domain; and   one of the polypeptide chains comprises V H 2-L3-V L 2 structure from N-terminus to C-terminus, wherein V H 2 is a heavy chain variable domain specifically binding to  K. pnewmoniae  O1 antigen; V L 2 is a light chain variable domain specifically binding to  K. pnewmoniae  O1 antigen; L3 is a peptide linker; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains;   or   (ii) wherein one of the polypeptide chains comprises V H 1-C H 1 structure from N-terminus to C-terminus, wherein V H 1 is a heavy chain variable domain specifically binding to  K. pneumoniae  O1 antigen; C H 1 is a heavy chain constant domain 1; wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains; and   one of the polypeptide chains comprises V L 1-C L  structure from N-terminus to C-terminus, wherein V L 1 is a light chain variable domain specifically binding to  K. pneumoniae  O1 antigen, C L  is a light chain constant domain; and   one of the polypeptide chains comprises V H 2-L3-V L 2 structure from N-terminus to C-terminus, wherein V H 2 is a heavy chain variable domain specifically binding to  K. pneumoniae  O2 antigen; V L 2 is a light chain variable domain specifically binding to  K. pneumoniae  O2 antigen; L3 is a peptide linker: wherein the polypeptide chain further comprises an Fc comprising C H 2 and C H 3 domains:   or   preferably, where the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 81, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 81; and   the amino acid sequence of SEQ ID NO: 82, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 82; and   the amino acid sequence of SEQ ID NO: 83, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 83;   or   (ii) the amino acid sequence of SEQ ID NO: 84, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 84; and   the amino acid sequence of SEQ ID NO: 82, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 82; and   the amino acid sequence of SEQ ID NO: 85, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 85:   or   more preferably, wherein the bispecific antibody comprises:   (i) the amino acid sequence of SEQ ID NO: 99, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 99; and   the amino acid sequence of SEQ ID NO: 100, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 100; and   the amino acid sequence of SEQ ID NO: 83, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 83:   or   (ii) the amino acid sequence of SEQ ID NO: 101, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 101; and   the amino acid sequence of SEQ ID NO: 100, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 100; and   the amino acid sequence of SEQ ID NO: 85, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 85.   
     
     
         52 . (canceled) 
     
     
         53 . (canceled) 
     
     
         54 . (canceled) 
     
     
         55 . (canceled) 
     
     
         56 . (canceled) 
     
     
         57 . A pharmaceutical composition, comprising:
 (i) the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O2 antigen according to  claim 2  and antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O1 antigen;   preferably, wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O2 antigen comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 11; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;   or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 10; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and/or   wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O1 antigen comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 35; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 41; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (b) a heavy chain variable domain (VH) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 36; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 42; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46;   or   (ii) the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to  claim 2  and a pharmaceutically acceptable carrier or adjunct;   or   (iii) a bispecific antibody comprising a first antigen-binding domain specifically binding to  K. pneumoniae  O2 antigen, and a second antigen-binding domain specifically binding to  K. pnewmoniae  O1 antigen, and a pharmaceutically acceptable carrier or adjunct;   wherein the first antigen-binding domain comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 11; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 10; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and/or   wherein the second antigen-binding domain comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 35; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 41; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 36; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 42; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46.   
     
     
         58 . (canceled) 
     
     
         59 . (canceled) 
     
     
         60 . The pharmaceutical composition of  claim 57 ,
 (a) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;
 and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises: 
 a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 35, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 41, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or 
   (b) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;
 and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises: 
 a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 36, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 42, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46; or 
   (c) wherein the antibody or antigen-binding fragment specifically binding to  K. pnewmoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 11, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;
 and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises: 
 a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 35, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 41, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or 
   (d) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 11, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;
 and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises: 
 a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 36, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a V L  comprising: an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 42, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46. 
   
     
     
         61 . The pharmaceutical composition of any one of  claim 57 , wherein the antibody or antigen-binding fragment specifically recognizing  K. pnewmoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:
 (a) a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24 or 33; or   (b) a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34;   and/or,   wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises:   (a) a V H  comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53; or   (b) a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54;   preferably, the pharmaceutical composition is selected from any one of (a), (b), (c) or (d):   (a) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34:   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53;   (b) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34:   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54;   (c) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24 or 33:   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53; or   (d) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO:24 or 33:   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (iii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54.   
     
     
         62 . (canceled) 
     
     
         63 . (canceled) 
     
     
         64 . (canceled) 
     
     
         65 . (canceled) 
     
     
         66 . (canceled) 
     
     
         67 . (canceled) 
     
     
         68 . An isolated nucleic acid molecule that encodes the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to  claim 2 . 
     
     
         69 . A vector comprising a nucleic acid molecule that encodes the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to  claim 2 . 
     
     
         70 . An isolated host cell comprising the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to  claim 2 . 
     
     
         71 . A method of producing the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to  claim 2 , comprising:
 a) culturing an isolated host cell comprising the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to  claim 2  under conditions effective to express antibody; and   b) obtaining the expressed antibody from the host cell.   
     
     
         72 . (canceled) 
     
     
         73 . A method of treating and/or preventing a disease or condition in an individual in need thereof, comprising administering to the individual an effective amount of:
 (i) the antibody or antigen-binding fragment specifically recognizing  K. pnewmoniae  O2 antigen according to  claim 2  and antibody or antigen-binding fragment specifically recognizing  K. pnewmoniae  O1 antigen:   preferably, wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O2 antigen comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 11; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 10; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and/or   wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O1 antigen comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 35; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 41; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 36; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 42; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46:   or   (ii) a bispecific antibody comprising a first antigen-binding domain specifically binding to  K. pneumoniae  O2 antigen, and a second antigen-binding domain specifically binding to  K. pneumoniae  O1 antigen, and a pharmaceutically acceptable carrier or adjunct;   wherein the first antigen-binding domain comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 11; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 1; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 10; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and/or   wherein the second antigen-binding domain comprises:   (a) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 35; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 41; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (b) a heavy chain variable domain (V H ) comprising a heavy chain complementarity determining region (HC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 36; an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38; and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a light chain variable domain (V L ) comprising a light chain complementarity determining region (LC-CDR) 1 comprising the amino acid sequence of SEQ ID NO: 42; an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44; and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46;   or   (iii) the antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen according to  claim 2 .   
     
     
         74 . The method of  claim 73 , wherein the disease or condition comprises one or more symptoms caused by  Klebsiella  infection;
 preferably, wherein the  Klebsiella  is  Klebsiella pneumoniae:      preferably, wherein the disease or condition comprises pneumonia, urinary tract infection, septicaemia/bacteremia/sepsis, neonatal septicaemia/bacteremia/sepsis, diarrhea, soft tissue infection, infection after organ transplantation, surgical infection, wound infection, lung infection, purulent liver abscess, lung abscess, cellulitis, necrotizing myositis, myositis, endophthalmitis, peritonitis, meningitis, necrotizing meningitis, ankylosing spondylitis or spinal Joint disease.   
     
     
         75 . (canceled) 
     
     
         76 . (canceled) 
     
     
         77 . The method of  claim 73 , wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O2 antigen and the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O1 antigen are administered to the individual concurrently or are administered to the individual consecutively. 
     
     
         78 . The method of  claim 73 , wherein in (i),
 (a) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 35, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 41, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (b) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 2, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 10, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 12, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 15;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 36, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 42, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46; or   (c) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 11, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 35, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 37, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 39; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 41, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 43, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 45; or   (d) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence SEQ ID NO: 1, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 4, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 6; and a V L  comprising an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 11, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 14, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 16;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising an HC-CDR1 comprising the amino acid sequence of SEQ ID NO: 36, an HC-CDR2 comprising the amino acid sequence of SEQ ID NO: 38, and an HC-CDR3 comprising the amino acid sequence of SEQ ID NO: 40; and a V L  comprising: an LC-CDR1 comprising the amino acid sequence of SEQ ID NO: 42, an LC-CDR2 comprising the amino acid sequence of SEQ ID NO: 44, and an LC-CDR3 comprising the amino acid sequence of SEQ ID NO: 46.   
     
     
         79 . The method of  claim 73 , wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:
 (a) a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24 or 33; or   (b) a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34;   and/or,   wherein the antibody or antigen-binding fragment specifically recognizing  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   (a) a V H  comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53; or   (b) a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54;   preferably,   (a) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53;   (b) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 20 or 29, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 20 or 29; and a V L  comprising the amino acid sequence of SEQ ID NO: 25 or 34, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 25 or 34;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54;   (c) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 24 or 33;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pnewmoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 47 or 51, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 47 or 51; and a V L  comprising the amino acid sequence of SEQ ID NO: 49 or 53, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 49 or 53; or   (d) wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O2 antigen in (i) or the first antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 19 or 28, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 19 or 28; and a V L  comprising the amino acid sequence of SEQ ID NO: 24 or 33, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO:24 or 33;   and wherein the antibody or antigen-binding fragment specifically binding to  K. pneumoniae  O1 antigen in (i) or the second antigen-binding domain in (ii) comprises:   a V H  comprising the amino acid sequence of SEQ ID NO: 48 or 52, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 48 or 52; and a V L  comprising the amino acid sequence of SEQ ID NO: 50 or 54, or a variant thereof having at least about 80% sequence identity to the amino acid sequence of SEQ ID NO: 50 or 54.